Table of Contents 7.5 Branching Trees 7.4 Classifying Organisms 7.3 Evolution of Species 7.2 Evidence of Evolution 7.1 Darwin’s Theory Chapter Preview

Chapter 7 Preview Questions 1.Compared to body cells, the cells that result from meiosis have a.half the number of chromosomes. b.the same number of chromosomes. c.double the number of chromosomes. d.triple the number of chromosomes.

Chapter 7 Preview Questions 1.Compared to body cells, the cells that result from meiosis have a.half the number of chromosomes. b.the same number of chromosomes. c.double the number of chromosomes. d.triple the number of chromosomes.

Chapter 7 Preview Questions 2. Which is true of the alleles for a gene? a.There are only two alleles for every gene. b.The alleles are always identical. c.The alleles are never identical. d.One allele may be dominant.

Chapter 7 Preview Questions 2. Which is true of the alleles for a gene? a.There are only two alleles for every gene. b.The alleles are always identical. c.The alleles are never identical. d.One allele may be dominant.

Chapter Preview Questions 3. An organism’s traits are determined by its a.carbohydrates. b.DNA. c.mitochondria. d.chloroplasts.

Chapter Preview Questions 3. An organism’s traits are determined by its a.carbohydrates. b.DNA. c.mitochondria. d.chloroplasts.

Chapter 7 Preview Questions 4. Where do sexually reproducing organisms inherit their alleles from? a.half from each parent b.mostly from their mother c.mostly from their father d.only from their mother

Chapter 7 Preview Questions 4. Where do sexually reproducing organisms inherit their alleles from? a.half from each parent b.mostly from their mother c.mostly from their father d.only from their mother

Section 7.1: Darwin’s Theory What important observations did Darwin make on his voyage? How did Darwin account for the diversity of species and the differences between similar species? How does natural selection lead to evolution? Changes Over Time

Darwin’s Voyage Charles Darwin sailed on the Beagle, from England to the Galápagos Islands. Changes Over Time

Darwin's Discoveries Galapagos Island Finches had beaks adapted to their diet Mainland Iguanas had short claws those on the islands had long claws

The flightless Galapagos cormorant has lost its ability to fly The size and shell shape of the tortoise differs between populations on different islands according to habitat.

The Theory of Natural Selection In 1859 Darwin proposed his theory of evolution based on the idea of natural selection. Natural Selection states that organisms adapt to their environment and that the strongest or most fit survive

Overproduction and Variation Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species. Changes Over Time

Competition and Selection Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce. Changes Over Time

Section 7.2: Evidence of Evolution What evidence supports the theory of evolution? How do fossils form? What do scientists learn from fossils?

Homologous Structures The structure of the bones in a dolphin’s flipper, a bird’s wing, and a dog’s leg is similar. Homologous bones are shown in the same color.

HOMOLOGOUS STRUCTURES Homologous structures: The structure of the bones in a dolphin’s flipper, a bird’s wing, and a dog’s leg is similar. Homologous bones are shown in the same color.

FOSSILES ARCHIOPTERIX

TRILOBITES

How Do Fossils Form? Most fossils form when organisms that die become buried in sediments.

Changes Over Time The fossils record provides evidence about the history of life and past environments on Earth. In addition, scientists use fossils to study the rate at which evolution has occurred.

Section 7.3: Evolution of Species What factors have contributed to the diversity of species? How do new species form? How do scientists infer evolutionary relationships among species? What causes the extinction of species?

Kaibab and Abert’s Squirrels These two kinds of squirrels have been isolated from one another for a long time. Eventually this isolation may result in two different species.

A Branching Tree This branching tree shows how scientists now think that raccoons, lesser pandas, giant pandas, and bears are related.

Extinction of Species Extinction is caused by a change in species' environment. The members of a species may not have adaptations that allow them to survive and reproduce in the changed environment.

Section 7.4: Classifying Organisms Why do biologists organize living things into groups? What do the levels of classification indicate about the relationship between organisms? What characteristics are used to classify organisms into domains and kingdoms?

Levels of Classification As you move down the levels of classification, the number of organisms decreases. The organisms at lower levels share more characteristics with each other.

Three Domains of Life In the three-domain system of classifications, all known organisms belong to one of three domains–Bacteria, Archaea, or Eukarya. ProtistsFungiPlantsAnimals Bacteria Archaea Eukarya

Section 5: Branching Trees How does a branching tree diagram show evolutionary relationships?

A Branching Tree Branching trees such as this show relationships between groups of organisms. It also shows the order in which specific characteristics may have evolved.

Shared Derived Characteristics A branching tree diagram shows evolutionary relationships by grouping organisms according to shared derived characteristics. Reptiles Amphibia ns Egg with shell Fishes Four limbs Backbone Invertebrate s Ancestor of animals